Saints took the lead in the first five minutes when Jay Rodriguez pounced on a poor back-pass by Michael Carrick and rounded a helpless David de Gea.

United hit back soon after through Wayne Rooney, before the England international secured the win with his second, but the visitors dominated proceedings following half-time and Sir Alex admitted his team rode their luck at times.

Speaking to MUTV, Ferguson said: "In my experience at the club, when we're going for championships there's always a game where you say to yourself: 'we were a bit lucky,' and I think this was one of those nights.

"I thought Southampton, in the second half, gave the best performance anyone's given here this season. I think they pushed right on top of us and didn't give us time to settle on the ball.

"On that surface the players are trying to take a touch, play their football and they found that difficult."

Sir Alex noted one major factor of his side's poor second-half performance, lamenting the state of the Old Trafford pitch on the back of a period of adverse weather in the area.

He continued: "In the second half, the players just found the pitch impossible. We tried to play the way we normally play and found it difficult because the pitch had dried out a lot. It was an ice cold night and it happens.

"First half, we lost an early goal but it didn't deter us from playing some fantastic football and we could have been four or five up at half time, but once the pitch started to dry out the players found it difficult to play a different way and it really required us to play the ball into the gaps, which we don't normally do.

"The pitch didn't help us. We can't use that as an excuse, but it didn't help us. It's a worry. We've won the game and I think that's the one thing we can take out of it."